Pressure generating devices for forcing reagents through filtering devices, absorption and chromatography columns have been in existence for many years. Most are expensive; some are motor pump operated and thus constitute complex systems. With the proliferation of small columns and cartridge filters for specific tests and analyses, a need has been created for a small, simple and inexpensive device to drive reagents through columns and filters. Sometimes a hand-held syringe or similar device can immediately pass a reagent through a column or filter (see U.S. Pat. No. 3,512,940) but very often the column is tightly packed or the filter has such a fine porosity that it becomes time consuming and tedious to use a hand-held syringe in this way.
Much of the developmental work in sample preparation for high performance liquid chromatography (HPLC), gas chromatography (GC) or filtration has been focused on increasing the speed, sensitivity, and efficiency of the techniques. Many of the classical techniques, such as centrifugation, dialysis and distillation, are labor-intensive, cumbersome, and prone to sample loss caused by multi-step manual manipulations.
Adjustable volume pipette samplers or syringes have been well known for years and are generally utilized in laboratories and medical facilities for accurately dispensing and/or aspirating precise volumes of samples including reagents, liquids to be sampled or analyzed, etc., particularly for use during HPLC, GC or other like sample preparation filtering processes. Many of these pipette devices include plunger stop-means, either integrally a part of the barrel of the pipette or adjacent the plunger, to limit the downward travel of the plunger, thus permitting an operator to dispense a precise volumetric quantity of liquid sample. Additionally, the prior art includes pipette samplers having axially adjustable barrels to permit the volumetric size of the barrel to either increase or decrease in volume capacity.
For example, U.S. Pat. No. 4,601,212 to the present inventor discloses a precision micropipettor including stop-means integral with the barrel finger flange to limit the downward and upward movement of the plunger by incorporating a longitudinally extending cut-away portion in the plunger, the cut-away portion acting to stop the plunger when the cut-away portion shoulders or ends abut with a horizontally extending pin embedded in the barrel finger flange. This device, while being an excellent product, does not permit delivery of a sample under pressure over time without constant attention by an operator or technician.
U.S. Pat. Nos. 3,675,492 to Tejera; 4,084,730 to Franke et al; and 4,117,728 to Johnson all disclose adjustable volume pipettes or syringes which include notched or stepped elements to limit upward or downward travel of the plunger, thereby allowing for the precise dispensing of a known volumetric quantity of liquid. However, these devices are unduly complex in structure as the Franke et al device, difficult to manufacture as the Tejera device, or both as the Johnson device. These devices also do not fully provide for limiting both upward and downward plunger movement, and in general do not permit delivery of a sample under pressure over a time span without operator attention.
The U.S. Pat. No. 4,526,294 to Hirshmann et al shows an axially adjustable barrel to limit the displacement of the plunger shaft reciprocally held therein; this device, also very structurally complex, suffers from many of the deficiencies noted above and below. Other patents disclosing devices of interest include Tervamaki et al U.S. Pat. Nos. 4,554,134; Oshikubo 4,591,072; and D'Autry 4,020,698.
While the above-mentioned patents show pipetting devices or the like having adjustable volume capabilities, at least most need extra mechanisms or devices to facilitate limiting of the plunger axial movement, and are expensive and cumbersome particularly when employing disposable type pipette samplers or syringes. Furthermore, no prior art pipette sampler is provided with self-contained or built-in pressure-generating means for forcing the sample into a filtering device or column, such as for use in conjunction with HPLC or GC, under a continuous known pressure, particularly without much assistance from an operator or technician.
Another problem which exists in the prior art is the unavailability of a simple structured pipette sampler which is so inexpensive that it can be thrown away after only a few uses without economic disadvantage. At the present time, adjustable volume pipettes are so expensive that throwing them away is not practical; in part this is so because of the needed presence of additional elements and the design and construction of other elements.
No adjustable volume pipette sampler has previously been available for allowing an experienced or inexperienced operator to reliably, rapidly and easily dispense therefrom and/or aspirate thereinto an accurate quantity of liquid repeatedly, constituting as well pressure-generating means for use in dispensing samples in conjunction with HPLC, GC, absorption columns, filters or whenever a measured sample must be forced into another device under a continuous predetermined pressure, particularly without much assistance from an operator or technician.
Additionally, there is a great need for a pressure-producing pipette sampler which prevents sample contact with the plunger to assure a contamination-free environment during subsequent sampling, as well as an indicia dual scale on the pipette barrel to indicate sample volume and sample pressure.
Attention is invited to copending application Ser. No. 894,809 which concerns somewhat related subject matter, the contents of such copending application being incorporated herein by reference.